Strain rate sensitivity of tensile properties in Ti–47Al–2Mn–2Nb–0.8TiB 2 alloy

Abstract

Strain rate sensitivity of tensile properties of Ti–47Al–2Mn–2Nb–0.8TiB 2 alloy with near lamellar (NL) microstructure were investigated within a strain rate range from 10 −5 s −1 to 10 3 s −1 using conventional static tensile testing technique, and a self-designed Split–Hopkinson tensile bar set-up with a rotating disk. Corresponding fracture surfaces at different strain rates were analyzed using a scanning electron microscope. It was found that tensile ductility fluctuates within a narrow range with the variation of the strain rate: dynamic elongation approximates to static elongation. But dynamic strengths σ d of the alloy are obviously higher than static strengths σ s; there exists a linear relationship between σ s and the logarithm of the strain rate ( σ s= A+ Bln ε ̇ ), but between dynamic strength σ d and the strain rate ( σ d= C+ D ε ̇ ). Fractography analysis indicates that the alloy fractures in a mixed mode of predominant transgranular cleavage and minor intergranular cracking under static and dynamic strain rates. Environmental effect is excluded from a main cause for the room-temperature brittleness of the investigated alloy.